数据库操作:公共的连接类

建立一个公共的连接类 ：GetConnection

package cn.xtnotes.unit;

import java.sql.Connection;
import java.sql.DriverManager;

public class GetConnetion {
	
	private static Connection conn =null;
	private static String address="jdbc:mysql://localhost:3306/data1?useSSL=false&serverTimezone=UTC"; 
	private static String dataBaseName="root"; 
	private static String dataBasePwd="123456";
	
	public static Connection getConn() {
		if(conn==null) {
			try {
				Class.forName("com.mysql.cj.jdbc.Driver");
				conn = DriverManager.getConnection(address,dataBaseName,dataBasePwd);
			} catch (Exception e) {
				System.out.println("链接失败");
				e.printStackTrace();
			}
		}
		return conn;
	}
}

conn=GetConnetion.getConn(); 链接数据库

package SQl;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

import cn.xtnotes.unit.GetConnetion;

public class Gongonglianjie {

	public static void main(String[] args) {
		Connection conn =null;
		conn=GetConnetion.getConn();
		String sql="select * from stu";
		Statement stmt=null;
		try {
			//Statement对象用来执行sql
			stmt = conn.createStatement();
			//执行sql并获取查询结果
			ResultSet rs=stmt.executeQuery(sql);
			while(rs.next()) {
				System.out.print("id:"+rs.getInt("id")+"---");
				System.out.print("name:"+rs.getString("name")+"---");
				System.out.print("age:"+rs.getInt("age")+"\n");
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally {
			try {
				conn.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
			try {
				stmt.close();
			} catch (SQLException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
	}
}